Jan
30
Part 1 of the centrifugal compressor efficiency series addressed the measurements and parameters that must be calculated to determine compressor efficiency. In Part 2-3 of this series we examined one way of calculating the enthalpy and entropy of the gas stream at the compressor suction and discharge and isentropic enthalpy for the refrigerant R134a. Once …
Jan
23
Part 1 of the centrifugal compressor efficiency series addressed the measurements and parameters that are used to calculate compressor efficiency. In Part 2 of this series we examine how these measurements are used to calculate the enthalpy of the gas stream at the compressor suction and discharged for the refrigerant R134a. This calculation utilized bilinear …
Jan
16
As addressed in Part 1 of the centrifugal compressor efficiency series, the enthalpy of the gas stream at the compressor suction and discharge must be known to determine the compressor efficiency. Also, the isentropic enthalpy must be determined based on the gas stream entropy at the compressor suction and the compressor discharge pressure. These properties …
Jan
09
Centrifugal compressors play an important role within the process industry. In some cases compressor capacity may determine the throughput of a plant. If a compressor is used for refrigeration then any variation in compressor operation may directly impact the temperature control in key unit operations such as flash vessels and exothermic reactors. Also, the compressor …
Nov
28
At Emerson Exchange, 2011, I had the pleasure of working with Frank Seibert, Technical Manager and Eric Chen, Associate Researcher, Pickle Research Center, University of Texas at Austin SRP and John Caldwell, Advanced Control Marketing Manage, and Willy Wojsznis, Senior Technologist, Emerson Process Management, to host a workshop that addresses how data analytics may be …
Nov
04
A secondary flow loop offers opportunities for feedforward control, identification of valve stick-slip and backlash, online metrics, diagnostics, rejection of pressure disturbances, linearization, and modeling. However, a secondary flow loop can be detrimental when the primary loop has a 63% response time less than 10 seconds. If the 63% response time is greater than 5 seconds, an exceptionally …
Aug
11
The product of the overall heat transfer coefficient and area (UA) determines the controllability of temperature processes. The deterioration of the UA is a particular concern for crystallization and polymerization processes. Frosting and fouling can decrease process efficiency and production rate even if the controllers are retuned. For exothermic reactors, a decrease in the UA …
Jul
28
Mixing changes the game. Mixing has a broad impact on disturbances, interactions, and noise. Mixing breaks paradigms on tuning, control, and performance. Mixing is at play in key unit operations offering incredible tightness of control and forgiveness of mistakes enabling exceptional product quality. I became sensitized to the role of mixing early in my career …
Jun
23
Automation engineers don’t get anywhere near the credit they deserve for increases in process performance. The value would be obvious if the automation system could be turned off but no one would allow this capture of the “before” and “after”. We need to do a better job of documenting where we are and could be. …
Jun
17
The greatest limitation I experienced as a user for process control improvement (PCI) was unmeasured process variables. If we had a high degree of instrumentation, so that only a configuration change was needed we could let our creativity roam free and quickly implement various improvements including new loops and feedforward control. Also, from trend charts …
